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The Herps of La Crosse

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Herps as Pets

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Northern Water Snake

(Nerodia sipedon)

Pictured above:  Adult and juvenile Water Snakes (top left and right).  Water Snake belly pattern (bottom right).

        Description: Northern Water Snakes are medium sized snakes, with adults reaching lengths of 24 to 41 inches (5 to 12 inches in juveniles).  They have tan or gray dorsal surfaces (ie, backs) that are crossed by reddish-brown, dark gray or black bands.  The lower jaw is usually off-white with darker bands running vertically, while their ventral surface (ie belly) is often covered with irregularly placed red blotches (pictured above).  Generally, these patterns are more distinct in juvenile specimens and tend to fade with age.  Furthermore, the reddish bands that are present in these snakes will often not be obvious in adults (making them appear to be a drab olive or gray color) unless they are wet.   The Northern Water Snake is a member of the family Colubridae and the sub-family Natricinae, which also includes garter snakes, brown snakes and red-bellied snakes.

        Habitat/Ecology: Water Snakes are very common near fresh water-bodies (ponds, lakes, rivers, etc.) with rocky shores and fallen logs that they can hide in and bask on.  They are also common near impoundments and diked rivers or streams.  Although they require much shore debris (ie, fallen trees with tangled root masses, large piles of rock), they seem to be found infrequently near  water-ways in forests (such as ephemeral wetlands).  I have also received reports of water snakes utilizing musk rat and beaver mounds as basking sites.  

    As their name suggests, these snakes are very agile swimmers and without hesitation will drop into the water from a basking spot to avoid danger (I have even found them resting completely submerged among the rip-rap that collects along the Mississippi River, with only their nostrils above the water).  Once in the water, they will either quickly swim to an adjacent shore to find safety or dive below the surface, only to reappear again far down stream.   

Vogt (1981) reports that mating occurs in May, immediately following emergence from hibernation.  Like several snake species in the sub-family Natricinae, water snakes give birth to live young (25 on average) in August/September.  They have been reported to hibernate in muskrat mounds and rocky hills adjacent to water.  I would suspect that they also hibernate in deep burrows or crevices (that go below the frost line) located along the shores of streams, rivers, etc., although no reports of this exist in Wisconsin.  

These snakes hunt fish, some invertebrates and amphibians.  Water Snakes are said to be preyed upon by wading birds, such as herons, raccoons and occasionally large fish.

        Remarks: Northern Water Snakes are common along the Mississippi River and its backwaters (and throughout the state near water ways).  Unfortunately, they are  often believed to be venomous Water Moccasins (which do not exist in Wisconsin outside of zoological gardens) and dangerous.  I have frequently been told stories by misinformed individuals who swear that they were aggressively chased by a water moccasin while swimming "up north" during a vacation.  Nothing could be further from the truth for Water Snakes are non-venomous and completely harmless.  Yet, this mistaken identity can result in many water snakes being wrongfully killed by swimmers, boaters and fisherman.   Furthermore, they are killed by fisherman who believe that they reduce game-fish populations (which is not true).  In fact, it has been suggested that Water Snakes may be beneficial to fish populations by consuming the sick, dying, or deformed individuals. 

These can be aggressive snakes if cornered, and will not hesitate to bite when threatened.  However, if left alone, they pose no threat to humans whatsoever.  Furthermore, they will readily dump their cloacal fluid (or defecate) on the person who has captured them.  This is incredibly unpleasant, and I can safely say (from personal experience) that very few snakes in Wisconsin have a more offensive smelling "musk" than the northern water snake.

        Water Snakes have been seen in the La Crosse River Marsh (Myrick Park Marsh), but not as commonly as Garter Snakes.  I have found dead individuals in several areas on the south side of La Crosse.  Most likely, this was the result of humans.  I have also found them in nearby Houston County (Minnesota).  

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